Pulse tube coolers and Gifford-McMahon coolers are used for cooling nuclear spin tomographs, cryo-pumps and other equipment. FIG. 1 (prior art) shows how a conventional gas compressor, such as a helium compressor, is used in combination with a rotary valve or with rotation valves. A helium compressor 10 is connected via a high-pressure line 11 and a low-pressure line 12 to a rotary valve 13. On the output side, the rotary valve 13 is connected via a gas line 14 to a cooling device 15 in the form of a Gifford-McMahon cooler or a pulse tube cooler. The high-pressure side and the low-pressure side of the gas compressor 10 are alternately connected via the rotary valve 13 to the pulse tube cooler or to the Gifford-McMahon cooler. The rate at which compressed helium is introduced into and removed again from the cooling device 15 is in the range of 1 Hz. A disadvantage of such cooler and compressor systems is that the motor-driven rotary valve 13 causes losses of about 50% of the input performance of the compressor.
Acoustic compressors or high-frequency compressors are also known in which one or more pistons are put in linear resonance oscillations by a magnetic field. These resonance frequencies are in the range of a few 10 Hz and are therefore not suitable for being used with pulse tube coolers and Gifford-McMahon coolers for generating very low temperatures in the range of less than 10 K.
A compressor device is therefore sought that is more efficient than the combination of a gas compressor and a rotary valve. In addition, a cooling device and a cooler unit are sought that incorporate such a compressor device.